Accurate ground-state calculations of mixed localized-itinerant materials with orbital-resolved Hubbard corrections to density functional theory

Hubbard corrections to density functional theory (commonly denoted DFT+U) can mitigate the impact of electron self-interaction that plagues semi-local exchange-correlation functionals. In doing so, they offer one of the most efficient ways to calculate the electronic structure of technologically relevant compounds containing transition-metal or rare-earth elements. An aspect of DFT+U that has so far escaped detailed scrutiny is the Hubbard manifold, that is, the subset of electronic states to which the Hubbard corrections are applied. Here, its definition is critically examined by showing that a broad class of materials—distinguished by the coexistence of localized and itinerant valence states—develops systematic errors when Hubbard corrections are assigned to the conventional atomic d- and f-shell manifolds. This insight forms the basis of an extended DFT+Hubbard scheme that enables the application of Hubbard corrections with orbital resolution, presented here as OR-DFT+U. Complemented by a linear-response approach for the non-empirical evaluation of the necessary Hubbard interaction parameters, this constitutes the main theoretical result of this work.